NOVA Science and Technology Book - 7 51Fact and ReasonWhy is a potato tuber used for cultivation? A potato tuber is a stem. It is used for cultivation because it can grow new plants. Memory Note1. Perennation is a process in plants, that helps them to survive during unfavourable conditions. 2. The spongy stem of aquatic plants helps in floatation and provides flexibility.Fact and ReasonThe stems of the cactus, opuntia, aloe, etc. are thick and fleshy. Why? The stems of the cactus, opuntia, aloe, etc. are thick and fleshy to store food and water. ActivityObserve the stem of various plants. 3.1.5 Leaf and its functionThe leaf is a flat green structure that grows from the stem or branches of the plant. Leaves contain a green pigment called chlorophyll. Dicots generally have short and broad leaves. Lamina is the flat green portion of the leaf. The leaf also contains a midrib that runs from the petiole to the leaf apex. Veins are present on either side of the midrib. They transport water, minerals and food in and out of the leaf. The arrangement of veins in a leaf is called venation. Leaves are modified for various purpose. For example, cactus leaves are modified into thorns to prevent loss of water. Water lily has broad leaves leaf
52 NOVA Science and Technology Book - 7that help the plant to float. Aloe Vera has a fleshy leaf. It stores food and water. The leaves of insectivorous plants (pitcher plants) modified to trap insects. Differentiate between leaf and root.S.N. Leaf S.N. Root1.The leaf is a flat green structure that grows from the stem. 1.The part of plant which helps to collect water and minerals is called the root. 2. It prepares food. 2. It absorbs minerals.Functions of leaf i. Leaves perform photosynthesis to prepare food and stores it. ii. The stomata present in the leaves take in carbon dioxide during photosynthesis and oxygen during respiration. iii. Stomata of leaves lose excess water in the form of water vapour by the process called transpiration. iv. It releases oxygen into the air. v. Leaves modified into thorns protect plants from herbivores. vi. Some plants propagate through leaves. leaf of pitcher plant traps insects leaf of fern produces spores leaf of Aloe Vera stores food and water Fact and ReasonSome plants bear thorns, or small leaves, why? Thorns or small leaves reduce the loss of water from plants by transpiration. So, some plants bear thorns or small leaves.
NOVA Science and Technology Book - 7 53Memory Note1. Venus flytrap is an insectivorous plant. Its leaves trap insects. 2. The leaf that is directly attached to the node without a petiole is called a sessile leaf.ActivityDivide yours class into four groups. Get a complete mustard plant for each group. Observe its vegetative parts and discuss with your friends and teacher.3.1.6 Flower and its functionFlowers are not present in non-flowering plants. Flowers are colourful reproductive parts of the flowering plant. Flowers have a sweet smell. Paddy has a very small flower. Some plants have large flowers. Flowers are available in different colours. The flower contains the reproductive part of the plant. The four main parts of the flower are calyx, corolla, androecium and gynoecium. Flower are modified for various purposes.Functions of floweri. The flowers produce sweet smell to attract insects for pollination.ii. It helps in the formation of the seed.iii. Some flowers produce foul smell to chase away insects.iv. Some flowers are modified to store food.StamenpistilantherstigmastyleovaryfilamentpetalsepalStructure of flowerComplete and Incomplete flowersThe flower that has all four parts, i.e., calyx, corolla, androecium and gynoecium is called a complete flower. Example: mustard flower.
54 NOVA Science and Technology Book - 7The flower which does not contain at least one of the four whorls is called an incomplete flower. Example: flowers of pumpkinCalyxThe group of sepals that forms the outermost whorl of a flower is called a calyx. It is usually green in colour. The calyx encloses and protects the flower during the budding stage and performs photosynthesis.CorollaThe coloured part formed by a group of petals is called the corolla. It is usually colourful. The corolla protects the reproductive organs during their development and attracts insects for pollination.Fact and ReasonWhy is the corolla scented? The corolla is scented to attract insects. Insects help in pollination. AndroeciumThe group of stamens or male reproductive parts of a flower is called androecium. A stamen has two parts: anther and filament. An anther is a top bi-lobed part of the stamen. It contains numerous small sacs called pollen sacs. The pollen sacs have tiny male reproductive units called pollen grains.GynoeciumThe group of carpels of a flower is called gynoecium. A pistil is divided into three different parts: stigma, style and ovary. Stigma is the uppermost part of the pistil which receives pollen grains. Style is a stalk that joins ovary and stigma. The ovary is the swollen part at the base of the pistil. It contains an ovule. The ovule holds the female reproductive cell called egg or ovum. Ovule after fertilization develops into seeds and ovary develops into fruit.Corollacarpel stamen
NOVA Science and Technology Book - 7 55Memory NoteRafflesia arnoldii is the largest flower found on the island of Indonesia. It is parasitic and has no distinct stems, leaves and branches. The flower is about 100 centimetres in diameter, and weigh up to 10 kilograms. Fact and ReasonWhy is a pumpkin flower called a unisexual flower? The pumpkin flower is called a unisexual flower because it lacks either androecium or gynoecium. Unisexual and BisexualA flower that contains only one reproductive part (either male or a female part) is called a unisexual flower. Examples are pumpkin, cucumber, etc. A flower that contains both male and female parts is called a bisexual flower. Examples are mustard, and sunflower.ActivityObserve the pumpkin flower. Which part is it missing? PollinationWhen a flower becomes mature, androecium releases pollen grains from its anther and pollen grains reach the stigma. The process of transfer of pollen grains (male gametes) from anther to stigma of a flower is called pollination. Insects are the most common agents that help in pollination.FertilizationFertilization is a process of union of a male gamete and a female gamete to form a zygote. The zygote develops into an embryo. An embryo is a multicellular structure formed by the cell division of a zygote. The fertilized ovule forms the seed. The embryo is the baby plant inside the seed.Memory NoteA zygote is the first cell of the baby plant, which is formed from the fusion of male and female gametes.
56 NOVA Science and Technology Book - 73.1.7 Fruit and its functionsThe non-flowering plants do not grow fruits. Gymnosperms also do not bear fruits. Fruits are present in angiosperm only. The fruit is a matured ovary. Wild animals feed upon fruits. Most of the fruits are edible. Some fruits are poisonous. Fruit is a good source of energy, minerals and vitamins for us. Different plants have different shapes, sizes, colours and tastes of the fruit. Fruits are fleshy. The fleshy part of the fruit is called the pericarp. It has three layers. Epicarp, mesocarp and endocarp are three layers of the fruit.Functions of fruitsIt stores food, protects seeds and helps in dispersal of seed.3.1.8 Seed and its functionsA seed is a ripened ovule of a flowering plant. Seeds of different plants have different shapes, sizes, colours and numbers. Seeds of angiosperm are enclosed in the fruit. Seeds of gymnosperm are on the cone.mango has one large seed apple has few seeds water melon has lots of tiny seeds Memory NoteThere is one cotyledon in a monocot, two cotyledons in dicot and one or more cotyledons in gymnosperms. Function of seed It stores food for embryo, protects embryo and helps in germination.
NOVA Science and Technology Book - 7 57Fact and ReasonWhy do seeds store food?Seeds stores food so that seedling can get nutrition after germination.Terms and Terminologies1. Root system : The part of the plant which grows inside the soil is called the root system.2. Shoot system : The part of the plant that grows above the soil is called the shoot system.3. Non-flowering plants : The plants that do not bear flowers are called non-flowering plants.4. Flowering plants : The plants that bear the flowers are called flowering plants.5. Root : The plant part which helps to collect water and minerals is called the root.6. Stem : The stem is the main support of the plant.7. Leaf : The leaf is a flat green structure that grows from the stem or branches of the plant.8. Venation : The arrangement of veins and veinlets in a leaf is called venation.9. Flowers : Flowers are colourful reproductive parts of the flowering plant.10. Complete flower : The flower that has all four parts, i.e., calyx, corolla, androecium and gynoecium is called a complete flower.11. Incomplete flower :The flower which does not contain at least one of the four whorls is called an incomplete flower.12. Calyx : The group of sepals that forms the outermost whorl of a flower is called a calyx.13. Corolla : The coloured part formed by a group of petals is called the corolla.14. Androecium : The group of stamens (male reproductive parts) of a flower is called androecium.15. Anther : An anther is a top bi-lobed part of the stamen.16. Gynoecium : The group of carpels of a flower is called gynoecium.17. Unisexual flower : A flower that contains only one reproductive part (either male or female part) is called a unisexual flower.18. Bisexual flower : A flower that contains both male and female reproductive parts is called a bisexual flower.19. Pollination : Pollination is a process of transfer of pollen grains (male gametes) from the anther to the stigma of a flower.
58 NOVA Science and Technology Book - 7Terms and Terminologies20. Fertilization : Fertilization is a process of union of a male gamete and a female gamete to form a zygote.21. Embryo : An embryo is a multicellular structure formed by the growth of a zygote.22. Fruit : The fruit is a matured ovary.23. Seed : A seed is a ripened ovule of a flowering plant.EXERCISESTEP 11. Fill in the blanks. water internode pollination stem zygotea. Corolla attracts insects for…………. b. The fusion of male and female gametes forms ………. c. The rhizome is the underground ……... d. The primary function of the roots is to collect ...... and minerals. e. The distance between two nodes is called an …………. 2. Tick the correct and cross the false statement. a. Calyx is a group of petals. b. Pumpkin plants bear unisexual flowers. c. The mustard plant has an incomplete flower. d. The stem holds all the structures of the root system. e. The leaf that has a petiole is called a petiolate leaf. 3. Choose the correct answer from the given alternatives. a. Which part of the plant grows above the soil? i. Taproot ii. Stem iii. Root hair iv. Root capb. Where do branches grow from? i. Roots ii. Apical bud iii. Nodes iv. Leaf
NOVA Science and Technology Book - 7 59c. What part helps in the growth of the height of the plant?i. Apical bud ii. Node iii. Root iv. Leaf d. What is the arrangement of veins on the leaf called? i. Root system ii. Shoot system iii. Venation iv. Node e. Which whorl of the flower can perform photosynthesis? i. Calyx ii. Corolla iii. Androecium iv. Gynoecium 4. Match the following Seed leafStigma matured ovuleAnther receives pollen grainKitchen of the plant petalSingle unit of corolla produces pollen grainSTEP 25. Answer the following questions in one word. a. What part of the plant grows under the soil? b. Which plant’s leaves are modified to trap insects? c. What is the term for a single unit of calyx? d. Which natural process produces a zygote? e. What is a matured ovary called? 6. Differentiate between the following. a. Leaf and root b. Stamen and pistil c. Calyx and corolla d. Unisexual flower and bisexual flower
60 NOVA Science and Technology Book - 7e. Pollination and fertilization 7. Give reason a. Pine trees have needle-like leaves. b. Eucalyptus plant have a huge fleshy stem. c. Desert plants have long roots. d. Aquatic plant have spongy roots and stems. 8. Study the given diagram and answer the following questions. B Ai. What is shown in the diagram? Write names of A and B. ii. Why is it called the male reproductive part? iii. Which part produces pollen grains? STEP 39. Answer the following questions. a. What are the functions of the root? b. What kinds of modifications are observed in leaves? c. Describe the major structure and functions of leaves. d. List a few functions of the stem. e. Name the whorls of a flower and list their functions. f. What is a zygote? How is it formed? g. What is a fruit? What are its functions? 10. Draw a well-labelled diagram of a complete flower.
NOVA Science and Technology Book - 7 61Unit 3.2 Invertebrates We see different types of animals around us. They differ in shape and size. Different types of animals have different features. Based on the presence or absence of backbone, the whole animal kingdom is divided into two subkingdoms. They are invertebrates and vertebrates.The animals which have a backbone (vertebral column) in them are called vertebrates. Fish, frogs, snakes, birds and dogs are examples of vertebrates.Invertebrates are animals that do not have a backbone in their body. Animals like a butterfly, spider, cockroach, dragonfly, mosquito, earthworm, roundworm, etc. are some of the examples of invertebrates.fig: examples of some classes of vertebrates Memory NoteThe backbone contains the spinal cord inside it. Characteristics of invertebratesi. They do not have a backbone or vertebral column in their body.ii. They are multicellular organisms except for protozoans.iii. They do not have a hard bony skeleton inside their body.iv. Some invertebrates have a hard exoskeleton on their body surface which is made up of a substance called chitin.v. They are less developed than the vertebrates.
62 NOVA Science and Technology Book - 7Fact and ReasonWhy do mosquitoes belong to subkingdom invertebrates? The mosquitoes belong to a subkingdom invertebrate because they do not have a backbone. Differences between vertebrates and invertebrates: S.N. Vertebrates S.N. Invertebrates1.The animals which have a backbone (vertebral column) in them are called vertebrates. 1.Invertebrates are animals that do not have a backbone in their body. 2. Vertebrates are more developed than invertebrates2. Invertebrates are less developed than vertebrates. 3.2.2 Classification of invertebratesThe invertebrates are classified into nine phyla. They are:1. Phylum Protozoa 2. Phylum Porifera3. Phylum Coelenterata 4. Phylum Platyhelminthes5. Phylum Nemathelminthes 6. Phylum Annelida7. Phylum Arthropoda 8. Phylum Mollusca9. Phylum Echinodermata1. Phylum protozoaThe word protozoa is derived from Greek words: protos and zoon. Protos means first and zoon means animals. This phylum consists of primitive unicellular organisms. The phylum of unicellular aquatic animals is called Protozoa. Protozoans are found in both fresh water and marine water. Some protozoans are found in moist soil and even as a parasite in different organisms. Amoeba, paramecium, plasmodium, euglena, etc. are protozoans.
NOVA Science and Technology Book - 7 63The characteristics of phylum Protozoa are:Amoeba Paramecium Euglena i. Most protozoans are aquatic.ii. They are unicellular microscopic organisms.iii. They move with the help of flagella, pseudopodia and cilia.iv. They breathe through the general body surface.v. They reproduce asexually by fission and sexually by conjugation.Fact and ReasonParamecium is called a protozoan, why? Paramecium is called a protozoan because it is a primitive unicellular and aquatic organism. ActivityObserve protozoans under the microscope. 2. Phylum PoriferaThe word porifera is derived from two Latin words: porous and fera. Porous means pore and fera means bearing. Porifera have numerous pores on their bodies. The numerous small pores present on their bodies are called Ostia. The large opening present at the tip is called osculum. The phylum of organisms that have pores in their body is called Porifera. Examples of poriferans are sponges like Euspongia, Spongilla, Sycon, etc.Sycon Euspongia Spongilla
64 NOVA Science and Technology Book - 7The characteristics of phylum Porifera are:i. They have numerous pores on their body.ii. Poriferans are mainly found in the marine (saltwater) habitat.iii. They are sessile. They are attached to the substratum like rocks.iv. Their body is asymmetrical.v. They can reproduce by both asexual and sexual methods.3. Phylum CoelenterataThe word coelenterate is derived from Greek words, kilos, which means hollow, and enteron, which means gut. Invertebrates that have hollow cavities or gut in their body are called coelenterates. Examples of coelenterates are jellyfish, hydra, sea anemone, etc.The characteristics of phylum Coelenterata are:Their body contains a hollow gut called coelenteron.i. They have a mouth but no anus.ii. They are found in marine habitats.iii. They are radially symmetrical animals. Their body can be divided into two halves by cutting them in many ways.iv. Their mouth is surrounded by tentacles. The functions of tentacles are protection and capturing food.v. They show both asexual and sexual reproduction.Memory Note1. Hydra lives in freshwater.2. The animal which has both male and female reproductive systems in a single body is called a hermaphrodite animal. Examples are earthworms and tapeworms.sea anemone jelly fish hydra coral
NOVA Science and Technology Book - 7 65Fact and ReasonHydra belongs to the phylum Coelenterata. Why?Hydra belongs to phylum Coelenterata because it has a hollow cavity in its body. 4. Phylum PlatyhelminthesThe word platyhelminthes is derived from two Greek words: platy, which means flat and helminth, which means worm. The phylum of invertebrates having a flat body is called Platyhelminthes.Some of the examples of platyhelminths are planaria, tapeworm, liver fluke, etc.The characteristics of phylum Platyhelminthes are:i. They have dorsoventrally flattened bodies.ii. They are mostly parasites. They have hooks or suckers or both to absorb the nutrients.iii. Flatworms have a thick cuticle that protects their body from the harmful enzymes of a host.iv. They have both segmented and unsegmented bodies.v. They can reproduce by both asexual and sexual methods.5. Phylum Nematoda/ Nemathelminthes/ AschelminthesThe word nematoda comes from the Latin word: nemat, which means thread and ode, which means like. Therefore, nematodes are organisms that have a thread like round body. Examples of nematodes are hookworm, pinworm, trichinella, ascaris, etc.whipworm roundworm hookworm planaria liver fluke tapeworm
66 NOVA Science and Technology Book - 7The characteristics of phylum Nemathelminthes are:i. They have a round, smooth and cylindrical body that is tapering at both ends.ii. Their body is covered by a protective cuticle.iii. They have a complete digestive system i.e.; they have both mouth and anus.iv. They are bilaterally symmetrical. Their body can be divided into two identical halves through mid.v. They are hermaphrodite organisms i.e., both male and female sex organs are present in the same body.Differentiate between a leech and a roundworm.S.N. Leech S.N. Roundworm1. A leech has a ring-like segment in its body. 1. A roundworm has a smooth body without rings.2. It is a parasite that lives outside of the human body.2. It is a parasite that lives inside the human body.6. Phylum AnnelidaAnnelida is derived from a Latin word annulus, which means little ring. The animals which belong to this phylum are called annelids. Therefore, annelids are animals that have rings (segments) on their body. They are also called segmented worms. Examples of annelids are earthworm, sandworm, leech, etc.leech earthworm sandworm
NOVA Science and Technology Book - 7 67The characteristics of phylum Annelida are:i. They have cylindrical, elongated and segmented body.ii. They have complete digestive system.iii. They have bilaterally symmetrical body.iv. They breathe through their body surfaces.v. They are unisexual or hermaphrodite. They reproduce sexually.Fact and ReasonEarthworms belong to phylum Annelida while tapeworms belong to phylum Platyhelminthes. Give reason. The earthworm belongs to phylum Annelida because its body is long and cylindrical with little rings. But the tapeworm belongs to the phylum Platyhelminthes because it has a long, segmented and flat body. Differences between tapeworm and earthwormS.N. Tapeworm S.N. Earthworm1. The tapeworm has a long, segmented and flat body.1. The earthworm has a long cylindrical body with little rings.2. It is a parasitic animal. 2. It is a free-living animal.7. Phylum ArthropodaIn Greek, arthros means joint and podos means foot. Animals that have jointed legs belong to this phylum. Arthropods have the highest number of species among all invertebrates. The phylum of invertebrates having jointed legs is called Arthropoda. They are found in all types of habitats in nature. Some of the examples of arthropods are spider, ant, butterfly, prawn, housefly, crab, scorpion, etc.centipede spider crab
68 NOVA Science and Technology Book - 7The characteristics of phylum Arthropoda are:i. They have a segmented body with jointed legs.ii. They are found in all types of habitats.iii. They have an exoskeleton made up of chitin.iv. Their body is bilaterally symmetrical and divided into head, thorax and abdomen.v. They have well developed digestive, circulatory and nervous systems.vi. They reproduce sexually.Fact and ReasonPhylum Arthropoda is the largest phylum. Why? Phylum Arthropoda is the largest phylum because arthropods are adapted to any kind of environment. They are found on land, in water, air, cold place, hot place and every where. ActivityGo to a garden and observe the types of insects or other arthropods that you see. Draw the diagrams of those animals and label them. Memory NoteInsects belong to the phylum Arthropoda. Insects are six-legged animals. There are over one million species of insects. 8. Phylum MolluscaThe word mollusca is derived from a Latin word mollis, which means soft. Animals belonging to this phylum have a soft body and they are called molluscs. The phylum of invertebrate organisms having a soft body is called Mollusca. Some examples of molluscs are slug, pila, squid, snail, oyster, octopus, etc.slug snail octopus
NOVA Science and Technology Book - 7 69The characteristics of phylum Mollusca are:i. They have a soft body covered by a hard shell.ii. They are found in marine water, freshwater as well as terrestrial habitats.iii. They often move with the help of strong muscular feet present on their ventral surface.iv. Their body is divided into head, visceral mass and foot.v. They reproduce sexually.Memory Note1. Phylum Mollusca is the largest marine phylum. About 23% of all marine organisms are molluscs. 2. The only hard body part of an octopus is a hooked beak at the end of its tentacles. 3. The term used for the animals having calcareous spines on their skin is Echinodermata.9. Phylum EchinodermataThe word echinodermata is derived from a Greek word echinos, meaning spiny and derma, meaning skin. Therefore, this phylum consists of animals that have rough spiny skin. The phylum of invertebrates having spines in their skin is called Echinodermata. Echinoderms are only found in salty or marine water. Hence, they are not found naturally in Nepal. Some examples of echinoderms are sea stars (starfish), sea urchins and sea cucumbers.sea urchin starfish sea cucumberThe characteristics of phylum Echinodermata are:i. They have a rough and spiny exoskeleton.ii. All echinoderms are marine organisms living mainly on the ocean floor.
70 NOVA Science and Technology Book - 7iii. They have tube feet for movement.iv. They have a complete digestive system.v. They have a radially symmetrical body.ActivityCollect some samples of invertebrates. Draw their labelled diagrams and list out their characteristic features. Terms and Terminologies1. Vertebrates : The animals which have a backbone (vertebral column) in them are called vertebrates.2. Invertebrates : Invertebrates are animals that do not have a backbone in their body.3. Protozoa : The phylum of unicellular, eukaryotic and aquatic animals is called Protozoa.4. Porifera : The phylum of organisms that have pores in their body is called Porifera.5. Coelenterates : Invertebrates that have hollow cavity or gut in their body are called coelenterates.6. Platyhelminthes : The phylum of invertebrates having a flat body is called Platyhelminthes.7. Nematodes : Nematodes are organisms that have a thread like round body.8. Annelida : Annelida is a group of invertebrates that have rings (segments) on their body.9. Arthropoda : The phylum of invertebrates having jointed legs is called Arthropoda.10. Mollusca : The phylum of invertebrate organisms having a soft body is called Mollusca.11. Echinodermata : The phylum of invertebrates having spines in their skin is called Echinodermata.
NOVA Science and Technology Book - 7 71EXERCISESTEP 11. Fill in the blanks with appropriate words.coelom backbone invertebrates unicellular radiallya) Animals that lack vertebral column are called ………………b) Vertebrates have ……………… in them.c) Protozoans are ……………… organisms.d) Coelenterates have hollow ……………… in their body.e) Starfish has ……………… symmetrical body.2. Write True for the correct and False for the incorrect statements.a. Hydra is an example of a cnidarian.b. A snail has a hard covering in its body.c. The earthworm has a round and unsegmented body.d. Octopus lies in the phylum Echinodermata.e. Arthropoda is a phylum with few species of invertebrates.3. Choose the correct answer from the given alternatives.a. Which phylum does a plasmodium belong to?i. Porifera ii. Protozoaiii. Arthropoda iv. Platyhelminthesb. What animals are called flatworms?i. Porifera ii. Protozoaiii. Platyhelminthes iv. Echinodermata
72 NOVA Science and Technology Book - 7c. Which phylum has a complete digestive system?i. Protozoa ii. Poriferaiii. Annelida iv. Echinodermatad. Which one is not a parasite?i. Tapeworm ii. Leechiii. Roundworm iv. Earthworme. Which one lives in the ocean only?i. Protozoa ii. Poriferaiii. Echinodermata iv. Mollusca4. Match the following.Invertebrate starfishProtozoa lacks backboneSubstratum unicellularLiver fluke spongesRadially symmetrical flat bodySTEP 25. Answer the following questions in one word.a. What is the sub-kingdom that contains organisms with backbones?b. What is the phylum of animals with lots of small pores on their body?c. What is the phylum of invertebrates with jointed legs?d. What is the phylum of animals with a soft body inside a hard shell?
NOVA Science and Technology Book - 7 73e. Name the phylum of animals that have a spiny exoskeleton.6. Write any two differences between:a. Vertebrates and invertebratesb. Poriferans and protozoansc. Hydra and starfishd. Earthworm and tapeworme. Coelenterates and molluscs7. Give reasons.a. Paramecium is a protozoan.b. Sponges are called porifera.c. Hydra belongs to the phylum Coelenterata.8. Write down the name of the following organisms and mention any one characteristic of each.a. b. c.c. d.
74 NOVA Science and Technology Book - 7STEP 39. Answer the following questions.a. What are vertebrates? Write its two special features.b. Define invertebrates. Write its two special features.c. What do you mean by a hermaphrodite animal?d. Write any four important features of the following phyla:i. Protozoa vi. Poriferaii. Coelenterata vii. Platyhelminthesiii. Nemathelminthes viii.Annelidaiv. Arthropoda ix. Molluscav. Echinodermatae. Name the phylum of animals having the following features and also give two examples of each:i. Pores are found all over the body surface.ii. Have a hollow cavity in the body and the mouth is surrounded by tentacles.iii. Dorsoventrally flattened worms.iv. The body is divided into head, thorax and abdomen.v. Radially symmetrical body with a spiny exoskeleton.10. Draw a diagram of the following animals and mention their phylum:a. Amoeba c. Hydrab. Snail d. Starfish
NOVA Science and Technology Book - 7 75Unit 3.3 The CellThe body of living organisms is made up of tiny building blocks called cells. Cells are the basic unit of life. They are responsible for performing living activities in organisms such as growth, reproduction, excretion, etc. The body of a living organism as a whole is the sum of the activities of all the cells. Hence, the cell is called a structural and functional unit of life. The word ‘cell’ was first coined by an English scientist named Robert Hooke in 1665 A.D.Fact and ReasonWhy is a cell called the structural and functional unit of life? A cell is called the structural and functional unit of life because the structure of an organism depends upon the number of cells. Also, everything performed by an organism is the outcome of the work done by the cells. Memory NoteRobert Brown discovered the nucleus of the cell. ActivityObserve plant tissues through the microscope. Memory Note1. Mycoplasma is the smallest cell. 2. Egg of the ostrich is the largest cell. ActivityMake a model of animal cells from reusable waste. microscope
76 NOVA Science and Technology Book - 73.3.1 Structure of a typical cellThe cell that lacks an organized nucleus is called a prokaryotic cell. Example: bacteria. The cell that has a well-organized nucleus is called eukaryotic cell. Organisms that are made of a single cell are called unicellular organisms. Examples: amoeba. Organisms that are made up of more than one cell are called multi-cellular organisms. Example: Cow, dog. Cells differ in shape, size and functions. Every cells contains cell organelles. Some of the important cell organelles are discussed below.a. Cell wallThe cell wall is the outermost tough covering of a plant cell. It is absent in an animal cell. The cell wall is mainly composed of non–living materials called cellulose. The cell wall maintains the rigidity of the cell. It is a permeable membrane.Functionsi. The cell wall protects the cell from external injuries.ii. It maintains the shape and size of the cell.b. Cell membraneCell membrane or plasma membrane is the semi-permeable membrane that surrounds the cell. It is made up of phospholipids and proteins. It is a thin and elastic membrane with numerous pores on it.
NOVA Science and Technology Book - 7 77Functionsi. It acts as a protective covering of a cell.ii. It helps in the selective transport of chemical substances in and out of the cell.Differences between the cell wall and cell membraneS.N. Cell wall S.N. Cell membrane1. The cell wall is made of cellulose.1. The cell membrane is made up of lipid and protein.2. The cell wall is dead and it is permeable.2. The cell membrane is living and it is semi-permeable.c. CytoplasmThe cytoplasm is the fluid-like substance that is present between the nucleus and the plasma membrane. Cell organelles float freely in the cytoplasmic fluid. It is made up of lipids, proteins, minerals and water.Functionsi. Cytoplasm maintains the turgidity of the cell.ii. It distributes nutrients and enzymes within the cell organelles.d. MitochondriaMitochondria are the rod or oval-shaped cell organelles that produce and store energy in the cell. Respiration occurs in mitochondria. This produces energy in the cell in the form of a chemical called adenosine triphosphate (ATP). So, mitochondria are also called the powerhouse of a cell.Functionsi. Mitochondria produce energy needed for various cellular activities.ii. They are also involved in the synthesis of smaller units of proteins called amino acids.mitochondria
78 NOVA Science and Technology Book - 7Fact and Reason1. Why are mitochondria called the powerhouse of the cell? Mitochondria are called the powerhouse of the cell because they perform cellular respiration to release energy and store it. 2. Bacteria is considered prokaryote. Why?Bacteria is considered prokaryote because it does not contain membrane bound well developed nucleus.e. NucleusThe nucleus is a double-layered round cell organelle that controls all activities of the cell. It contains nuclear membrane, chromatin fibres, nucleolus and nucleoplasm. The nuclear membrane is the outermost covering of the nucleus. A dark and round spot inside the nucleus is called the nucleolus.Functionsi. The nucleus controls the metabolic activities in the cell. So, it is also called the control centre.ii. The DNA present in the nucleus helps to transfer the hereditary information from the parents to the offspring.Memory Note1. The nucleus dissolves into the cytoplasm during cell division. 2. Mitochondria help in internal respiration.f. VacuolesVacuoles are the membrane-bound sap filled structure present in the cytoplasm. The fluid inside the vacuole is called cell sap. The outer covering of the vacuole is called tonoplast. A plant cell has a large central vacuole while an animal cell has many smaller vacuoles.Functioni. The vacuole stores water, sugar, salts and other waste materials of the cell.ii. The space inside the vacuole helps to maintain the turgidity of the cell.Nucleus
NOVA Science and Technology Book - 7 79g. PlastidsPlastids are the disc-shaped double-layered cell organelles found only in plant cells. There are three kinds of plastids. They are chloroplast, chromoplast and leucoplast.Functionsi. Chloroplasts help to trap sunlight for photosynthesis.ii. Chromoplasts help to ripen fruits and provides colour to the flowers.iii. Leucoplasts are involved in the synthesis of starch, oils and proteins.Chloroplast Chromoplast Leucoplast Memory NoteAnimal cells do not have plastids. Fact and ReasonThe chloroplast is called the kitchen of the cell. Give reason. The chloroplast is called the kitchen of the cell because it prepares the food needed for the plant.h. Endoplasmic reticulumThe endoplasmic reticulum is the branching tubules and flattened sacs that extend throughout the cytoplasm. It provides mechanical support to the cell.Functioni. Rough endoplasmic reticulum transports proteins to various parts of the cell.ii. Smooth endoplasmic reticulum helps in lipid formation.Endoplasmic reticulum
80 NOVA Science and Technology Book - 7i. Golgi bodyGolgi bodies are a network of flattened layers of membrane-bound sacs. They are located near the nucleus.Functioni. They store, package, and distribute the proteins and lipids made in the endoplasmic reticulum.ii. They also manufacture substances like cellulose and pectin.j. RibosomeRibosomes are small granular structures that float freely in the cytoplasm or are bound to the endoplasmic reticulum. Ribosome synthesis proteins.k. LysosomeLysosomes are membrane-bound sacs that contain digestive enzymes. If the lysosome breaks open, the enzymes can destroy the cell by digesting the cell organelles. So, it is also called a suicidal bag.Functioni. Lysosomes help in intracellular digestion.ii. They engulf viruses or bacteria and protect the cell organelles from foreign bodies.Fact and ReasonLysosomes are called suicidal bags because if the lysosome breaks open, the enzymes can destroy the cell by digesting the cell organelles with their digestive enzymes. l. CentrosomeThe centrosome is pair of tubular organelles that are found near the nucleus. They help in cell division. They are not present in plant cells. They look like stars.centrosome
NOVA Science and Technology Book - 7 81ActivityTo observe onion cells under a compound microscope.Take an onion and cut a small section of it. Peel a thin transparent layer. Transfer the slice of a thin layer into the glass slide. Add a drop of saffron for colour. Observe the slice under a compound microscope.Differences between the cell wall and cell membraneS.N. Plant cell S.N. Animal cell1. The plant cell is usually larger than an animal cell.1. An animal cell is comparatively smaller in size.2. It has a cell wall. 2. It does not have a cell wall.3. Plastids are present in the plant cell.3. Plastids are absent in an animal cell.4. It contains a large central vacuole.4. It contains many small vacuoles.5. The nucleus lies on one side in the peripheral cytoplasm.5.The nucleus lies at the centre.6. Centrioles are usually absent.6. Centrioles are present.7. Reserve food is in the form of starch.7. Reserve food is in the form of glycogen.8. Lysosomes are rare. 8. Lysosomes are always present.Terms and Terminologies1. Cells : Cells are tiny building blocks of living organisms.2. Prokaryotic cell : The cell that lacks an organized nucleus and other membranebound cell organelles is called a prokaryotic cell.3. Eukaryotic cell : The cell that has a well-organized nucleus and membrane bounded cell organelles is called a eukaryotic cell.4. Unicellular organisms : Organisms that are made of a single cell are called unicellular organisms.5. Multicellular organisms : Organisms that are made up of more than one cell are called multicellular organisms.6. Cell wall : The cell wall is the outermost tough covering of a plant cell.
82 NOVA Science and Technology Book - 7Terms and Terminologies7. Cell membrane : Cell membrane or plasma membrane is the semi-permeable membrane that surrounds the cell.8. Cytoplasm : The cytoplasm is the fluid-like substance that is present between the nucleus and the plasma membrane.9. Mitochondria : Mitochondria are the rod or oval-shaped cell organelles that produce and store energy in the cell.10. Respiration : Respiration is the process by which energy is produced by utilizing food and oxygen in the cell.11. Nucleus : The nucleus is a double-layered round cell organelle that controls all activities of the cell.12. Nucleolus :A dark and round structureinside the nucleus is called the nucleolus.13. Vacuoles : Vacuoles are the membrane-bound sap filled structure present in the cytoplasm.14. Tonoplast : The outer covering of the vacuole is called tonoplast.15. Plastids : Plastids are the disc-shaped, double-layered cell organelles found only in plant cells.16. Endoplasmic reticulum : The endoplasmic reticulum is the branching tubules and flattened sacs that extend throughout the cytoplasm.17. Golgi bodies : Golgi bodies are a network of flattened layers of membrane-bound sacs.18. Ribosomes : Ribosomes are small granular structures that produces protein.19. Lysosomes : Lysosomes are membrane-bound sacs that contain digestive enzymes.20. Centrosome : The centrosome is pair of tubular organelles that are found near the nucleus.EXERCISESTEP 11. Fill in the blanks.nucleus chromoplast prokaryotic mitochondria proteina. Bacteria have ……………cells.b. Energy is produced by ………… in the cell.c. The control centre of the cell is……….d. Flowers are colourful because of the presence of………….e. Ribosomes synthesise …………
NOVA Science and Technology Book - 7 832. Tick the correct and cross the false statement.a. A single cell contains all the vital structures and substances for its independent function.b. The main material of the cell wall is wax.c. Lysosomes are called suicidal bags of the cell.d. Vacuoles synthesize proteins.e. Golgi bodies manufacture cellulose and pectin.3. Choose the correct answer from the given alternatives.a. Which one is a prokaryotic organism?i. Paramecium ii. Hydraiii. Bacteria iv. Amoebab. What is the largest cell?i. Ostrich egg ii. Amoebaiii. Red blood cell iv. White blood cellc. Which is the energy produced in mitochondria?i. ATP ii. DNAiii. RNA iv. APTd. Which organelle is capable of digesting even the cell organelles?i. Ribosome ii. Nucleusiii. Mitochondria iv. Lysosomee. Which one of the given cell organelles is non-living?i. Mitochondria ii. Cell walliii. Nucleus iv. Plastids4. Match the followingCell wall Control centre of the cell Cell membrane Cell sap Nucleus Cell divisionCellulose PlasmalemmaCentrosome Vacuole
84 NOVA Science and Technology Book - 7STEP 25. Answer the following questions in one word.a. Which material makes the cell wall?b. Which plastid is colourless?c. Which plastid helps in photosynthesis?d. What is the outermost layer of the plant cell called?e. Name the site for the production of energy in the cell.6. Differentiate between the following.a. Cell wall and cell membraneb. Unicellular organisms and multicellular organismsc. Eukaryotic cell and prokaryotic cell7. Give reason.a. The chloroplast is the kitchen of a plant cell.b. The euglena is a unicellular organism.c. The lysosome is called a suicidal bag.d. Mitochondria are the powerhouse of the cell.8. Identify the cell organelles and write their major functions.STEP 39. Answer the following questions.a. What is a cell? Who discovered it?b. How is a cell in our body different from the cell of bacteria?c. List any three functions of the cell membrane.d. Write a short note on mitochondria.e. What is the importance of the nucleus?f. What is the endoplasmic reticulum? Write its functions.10. Draw a well-labelled diagram of the animal cell.
NOVA Science and Technology Book - 7 85A.G. Tansley (1871–1955) was a distinguished British ecologist and botanist. He is known for his important contributions to ecology. He is credited with coining the term “ecosystem”. It describes the complex interactions between living organisms and their physical environment. Tansley’s research focused on plant ecology and biodiversity. He also played a key role in establishing the British Ecological Society. A.G. TansleyAbout the inspiring scientistObserve plants, animals, and natural resources of Koshi Tappu Wildlife Reserve in the given photos. Now, answer the following questions.Questionsi. Why do you think Koshi Tappu Wildlife Reserve is rich in biodiversity? ii. Why should we avoid human encroachment in the wildlife reserve? iii. The wildlife reserve has many swamps, lakes, and rivers. How do they benefit the ecosystem and human beings?iv. What can we do to protect biodiversity and other natural resources? WARM UP ACTIVITYBIODIVERSITY AND ENVIRONMENTEstimated Teaching Periods TH PR8 24
86 NOVA Science and Technology Book - 74.1 BiodiversityThe existing number of living organisms in a particular area is called biodiversity. Plants and animals are important components of the environment. All plants are not the same; they vary from each other. Bacteria, fungi, algae, mosses, pteridophytes, angiosperms, monocots, and dicots are different groups of plants. Animals can be divided into several different groups like invertebrates, vertebrates, fishes, amphibians, reptiles, and mammals. Each individual of these groups also differs from the other. This variability among living beings and within living beings is called biodiversity or biological diversity. Biodiversity Fact and ReasonHuman activities are a threat to biodiversity. Give reason. Human activities are a threat to biodiversity because our activities such as urbanization, poaching, deforestation, etc. have forced different species of biodiversity to be endangered, rare and even extinct. Memory NoteThere are three types of biodiversity, ecosystem diversity, genetic diversity and species diversity.
NOVA Science and Technology Book - 7 874.2 EnvironmentThe group of living things and non-living things around us is called the environment. We get oxygen, food and shelter from the environment. We receive water from different sources like wells, tube wells, taps and rivers. We tame animals and grow crops on the land. We are capable of producing energy from different sources like water, fossil fuels, sun, wind, etc. We use medicinal herbs from forests to manufacture medicines. But, while doing development activities, we are degrading the environment and over exploiting natural resources. As a result there is an environmental imbalance. Natural disasters and epidemics are occurring frequently and resources are scarce. At this rate earth won’t be suitable for living things to live anymore. Therefore, conserving the environment and its resources is very important. environmental degradationActivityMake a list of activities that happen in your community that are harming the environmenSome of the ways to conserve the environment are: i. Prevent deforestation and encourage afforestation.
88 NOVA Science and Technology Book - 7ii. Control air, water and land pollution. iii. The concept of reduce; reuse and recycle should be adopted. iv. Vehicles and industries that produce more smoke should be banned. v. We should not use chemical fertilizers and insecticides. 4.3 Natural resourcesResources that are directly provided by the nature itself are called natural resources. Natural resources like air, water, sunlight and land are the most essential resources for the survival. Other natural resources like forests, wildlife, minerals, etc. are used to meet the survival needs and to satisfy the demand of life. ActivityPeople in rich countries consume 10 times more natural resources than people in poor countries. Types of natural resources There are two types of natural resources. They are renewable resources and non-renewable resources. Fact and ReasonSunlight is a renewable natural resource, why? Sunlight is a renewable natural resource because it is perpetual. It can be obtained on the earth forever. a. Renewable natural resources Those resources that are unlimited or can be renewed or reproduced even after they are finished are called renewable resources. Plants, animals, air, water, sunlight and fertile land are examples of renewable resources. Some of them are perpetual but some get scarce if overused.plant animals water
NOVA Science and Technology Book - 7 89Fact and ReasonWhy is grass an example of a renewable resource? The grass is an example of a renewable resource because it can regrow again even after cutting or grazing. Memory NoteRenewable natural resources also produce clean energy. b. Non-renewable natural resources Those resources that cannot be renewed or reproduced after they are finished are called non-renewable resources. Metallic and nonmetallic minerals, diesel, petrol, natural gas and coal are examples of non-renewable resources. Once these natural resources are depleted, they cannot be regenerated within the human time scale as they take more than thousands or millions of years to get deposited back in nature. coal LPG petroleum Fact and ReasonMinerals and fuels should be used wisely, why?Minerals and fuels should be used wisely because these are nonrenewable resources.Differences between the renewable resources and non-renewable resourcesS.N. Renewable source S.N. Non-renewable source 1. Those resources that can be renewed or reproduced even after they are finished are called renewable resources. 1. Those resources that cannot be renewed or reproduced after they are finished are called non-renewable resources.
90 NOVA Science and Technology Book - 7S.N. Renewable source S.N. Non-renewable source 2. Renewable resources can be regenerated. Examples: forest, water, etc. 2. Non-renewable resources cannot be regenerated. Examples: coal, petrol, etc.Importance of natural resources Natural resources are the backbone of mankind and development. The importance of natural resources is mentioned below: i) Food: Environment provides food for all life forms. Photosynthesis is source of food in the environment. ii) Fresh air: Photosynthesis in plants not only provides food, but also oxygen. Oxygen is needed for all living beings for respiration. iii) Water: All living beings including humans obtain water from nature. iv) Habitat: Some organisms live on forest, meadow, hills, burrow, water and land. v) Fuels and minerals: Different sources of fuel like wood, uranium, coal, petrol, and natural gas come from nature. Minerals like gold, limestone, iron, and copper that are needed for infrastructure development also come from nature. vi) Income: Protected natural resources like national parks and wildlife reserves, beautiful places like rivers, mountains, valleys and gorges attract domestic and foreign tourists. This also helps in the economic growth of the country through the collection of revenue.
NOVA Science and Technology Book - 7 91tourists visit national parks for site seeing and viewing animalsDepletion of natural resourcesWe are continuously exploiting natural resources to meet our needs and demands. Our activities are increasing environmental pollution. We throw garbage, vegetable wastes, wastewater, etc. on land and in water. Our industries, factories and vehicles add smoke and harmful chemicals to the air every day. We, humans, are overusing fertilizers, insecticides and chemicals. Our cities have been excessively urbanized and industrialized. The rate of deforestation is also higher. Due to these various activities, natural resources are depleting day by day. Thus, we can say that human beings are responsible for the depletion of natural resources.forest fire deforestation pollutionfig: causes of depletion of natural resourcesCauses of the depletion of natural resourcesi. Rapid population growth and uncontrolled migrationii. Unmanaged urbanization and industrializationiii. Deforestation and forest fireiv. Environmental pollutionv. Use of fossil fuel
92 NOVA Science and Technology Book - 7Conservation of natural resourcesThe best way of conserving natural resources is by limiting their overuse and sustainably using them. Allocating protected areas, harvesting forests scientifically, afforestation, reforestation, and controlling pollution can conserve natural resources in the long term.4.4 Water resourcesThe sources of water like rivers, ponds, lakes and sea, which are useful to the living organisms in various ways, are called water resources. About 97% of all water on the earth’s surface is ocean water. The freshwater of rivers, ponds, lakes, etc. is only about 3%. The freshwater of the earth is stored in glaciers, mountain caps, rivers and groundwater.Sources of waterSurface water, groundwater and rainwater are three different sources of water. Water that is available on the surface of the earth like springs, streams, rivers, ponds and lakes is called surface water. Water that comes from rain is called rainwater. Water under the surface of the earth is called groundwater. Nepal is rich in water resources as it has a large number of rivers and lakes that are formed by icy mountains.lake river well tube well fig: sources of waterMemory NoteRainwater, groundwater and surface water are the main sources of water. Fact and ReasonNepal is rich in water resources, why? Nepal is rich in water resources because of summer monsoon and the snow stored in the Himalayan range which gives rise to many rivers, lakes, etc.
NOVA Science and Technology Book - 7 93ActivityList the water resources available in your locality. Categorize them as surface water, groundwater and rainwater sources and list the purposes of using such water. 4.5 WatershedA watershed is an area that drains the water from the rain and melted snow into water bodies like rivers and lakes. The size of a watershed may vary from place to place. Example: Shivapuri watershed, Indra Sarovar and Bagmati watershed.WatershedWetlands are the areas filled with water temporarily or throughout the year. Aquatic plants, shrubs or trees grow in it. In simple words, wetlands are marshy or swampy areas of land with moist soil or soil covered with water. Example: Fewa lake, Koshi Tappu, etc.Fact and ReasonWatersheds are very important for preventing the depletion of groundwater. Watersheds absorb water during the rainy season. Destruction of watersheds will cause more amount of runoff and a decrease in groundwater level. Thus, watersheds are very important for preventing the depletion of groundwater.
94 NOVA Science and Technology Book - 7Memory NoteThe amazon river watershed is the largest watershed in the world. 4.6 WetlandWetlands are the areas filled with water temporarily or throughout the year. Aquatic plants, shrubs or trees grow in it. In simple words, wetlands are marshy or swampy areas of land with moist soil or soil covered with water. Example: Fewa lake, Koshi Tappu, etc. WetlandDifferentiate between wetland and watershed. S.N. Wetland S.N. Watershed1. Wetland is the area filled with water temporarily or throughout the year. 1. A watershed is an area that drains the water from the rain and melted snow into the water bodies like rivers and lakes. 2. Wetlands are the homes of many plants and animals. 2. Watershed gives birth to the river. Importance of wetland and watershedWetlands are not only important for animals and plants, but they are very important for humans as well. Below are some of the major importance of wetlands.i. Wetlands and watershed are homes of many plants and animals.
NOVA Science and Technology Book - 7 95ii. The plants in the wetlands give us food and medicines.iii. Animals found in the wetlands like fishes provide food for us.iv. Wetlands are the sources of water for domestic purposes, industrial processes, hydroelectricity, and irrigation.v. They attract tourists and generate national income.vi. Wetlands control floods by storing excess flood water.vii. Wetlands maintain the natural environment and beauty of the place.ActivityVisit a nearby wetland with guardian and list the names of four major animals, birds and plants each found in that wetland. Memory NoteWetlands cover nearly 5% area of our country. Conservation of water resources, watershed and wetlands Different types of human activities like deforestation, pavement tiling, water pollution, and urbanization have affected watersheds badly.Some of the ways to conserve watersheds are:i. Government should declare watershed areas as protected areas.ii. Deforestation should be stopped and encourage afforestation.iii. Plotting cultivable land for settlement areas should be stopped.iv. Water pollution should be controlled.v. Drainage should be built in urban areas.Fact and ReasonWe should protect the forest of Nepal. Why? We should protect the forests of Nepal because forest will protect watershed, wildlife, and environment.4.7 Management of solid wasteEnvironment sanitation means maintaining clean and healthy surroundings that are needed for a healthy life. Wastes like plastics, papers, scrap metals, clothes, food wastes, and wastewater from the kitchen and bathroom
96 NOVA Science and Technology Book - 7degrade environment. We need to maintain environmental sanitation by managing the waste. Some of the ways to manage waste are composting, burning, and landfilling. Waste management locally at the source level is very cheap and easy to practice if we follow the ‘3R Principle’. 3R means reduce, reuse and recycle.ReduceReduce means to decrease the amount of waste. We should use resources only in the required amount. The resources should not be overexploited.ReuseReuse means the use of the same material times and again. Materials should be reused again as far as possible. This limits the amount of waste in the community. For example, plastic wrappers can be used for decoration. Used plastic containers and bottles can be reused as small plant vases. Waste paper can be used to make envelopes.RecycleRecycling means changing or modification of materials into new ones. Non-degradable wastes can be recycled. Plastic, paper, glasses, and metals can be recycled. Recycle of materials reduces the consumption of raw materials. Applying the 3R principle does not only lead to a clean environment but also controls the overuse of natural resources. It also saves time and money that is spent on managing waste.reducereuserecycle
NOVA Science and Technology Book - 7 97Memory NoteOne recycled aluminium can save enough energy to light ten 100-watt bulbs for one hour. Terms and Terminologies1. Biodiversity : The existing number of living organisms in a particular area is called biodiversity.2. Environment : The group of living things and non-living things around us is called the environment.3. Natural resources : Resources that are directly provided by the nature itself are called natural resources.4. Non-renewable resources : The resources that cannot be renewed or reproduced after they are finished are called non-renewable resources.5. Renewable resources : The resources that are unlimited or can be renewed or reproduced even after they are finished are called renewable resources.6. Water resources :The sources of water like rivers, ponds, lakes and sea, which are useful to the living organisms in various ways, are called water resources.7. Surface water : The water which is available on the surface of the earth like springs, streams, rivers, ponds, lakes, etc. is called surface water.8. Ground water :The water which is available under the surface of the earth is called groundwater.9. Watershed :A watershed is an area that drains the water from the rain and melted snow into water bodies like rivers and lakes.10. Wetland : Wetlands are the areas filled with water temporarily or throughout the year.11. Environment sanitation : Environment sanitation means maintaining clean and healthy surroundings that are needed for a healthy life.12. Reduce waste : Reduce means to decrease the amount of waste.13. Reuse waste : Reuse means the use of the same material repeatedly.14. Recycling : Recycling means changing or modification of waste materials into new ones.
98 NOVA Science and Technology Book - 7EXERCISESTEP 11. Fill in the blanks.non-renewable wetland biodiversity groundwater renewablea. Marshy and swampy land is called ……………….b. The existing number of living organisms in a particular area is called ……….c. Water under the surface of the earth is called ………….d. Plants, air, water, fertile land, etc. are ……. resources.e. Minerals, diesel, petrol, coal, etc. are ……….resources.2. Tick the correct and cross the false statement.a. Fossil fuel is a renewable natural resource.b. Biodiversity is the term used to describe the variety of life found on the earth.c. Resources that are directly provided by nature itself are called natural resources.d. Petroleum products are used for many purposes like running vehicles and industries, burning, etc.e. Natural resources are the backbone of mankind and development.3. Choose the correct answer from the given alternatives.a. Which one is a renewable natural resource?i. Solar energy ii. Petroliii. Both iv. Coalb. What type of natural resource is forest?i. Watershed ii. Renewableiii. Non-renewable iv. Firewoodc. Arya carried water in the bottle of coke. What kind of activity is it?i. Reduce ii. Reuseiii. Recycle iv. Watershed
NOVA Science and Technology Book - 7 99d. What type of natural resource is petroleum?i. Expensive ii. Renewableiii. Non-renewable iv. Liquide. Which one is a non-renewable natural resource?i. Water ii. Coaliii. Air iv. Sunlight4. Match the following:Surface water recycleRenewable natural resource pondNon-renewable natural resource airPlaces that supply water into river fossil fuelsConversion of waste into goods watershedSTEP 25. Answer the following questions in one word.a. Give an example of wetland.b. What kind of natural resource is air and water?c. What kind of natural resource regenerate over time?d. What kind of natural resource does not regenerate?e. Give an example of non-renewable natural resource.6. Differentiate between the following.a. Renewable resources and non-renewable resourcesb. Wetland and watershed7. Give reason.a. Grass is an example of a renewable resource.b. Petroleum should be used wisely.c. Nepal is rich in water resources.
100 NOVA Science and Technology Book - 78. Study the given diagram and answer the following question.i. What is the type of natural resource shown in diagram?ii. Why should we have these resources near the watershed?STEP 29. Answer the following questions.a. Mention any four importance of natural resources.b. Describe the role of human beings in the conservation of the environment.c. Natural resources are depleting in our country. What activities lead to the depletion of natural resources? Explain.d. List the importance of water resources.e. What can we do to protect the watersheds of our country?